"""EpochConverter module containing class EpochConverter."""

import numpy as np

import matplotlib.units as units
import matplotlib.dates as date_ticker

__all__ = ['EpochConverter']


class EpochConverter(units.ConversionInterface):
    """: A matplotlib converter class.  Provides matplotlib conversion
          functionality for Monte Epoch and Duration classes.
    """

    # julian date reference for "Jan 1, 0001" minus 1 day because
    # matplotlib really wants "Jan 0, 0001"
    jdRef = 1721425.5 - 1

    @staticmethod
    def axisinfo(unit, axis):
        """: Returns information on how to handle an axis that has Epoch data.

        = INPUT VARIABLES
        - unit     The units to use for a axis with Epoch data.

        = RETURN VALUE
        - Returns a matplotlib AxisInfo data structure that contains
          minor/major formatters, major/minor locators, and default
          label information.
        """

        majloc = date_ticker.AutoDateLocator()
        majfmt = date_ticker.AutoDateFormatter(majloc)

        return units.AxisInfo(majloc=majloc, majfmt=majfmt, label=unit)

    @staticmethod
    def float2epoch(value, unit):
        """: Convert a matplotlib floating-point date into an Epoch of the
              specified units.

        = INPUT VARIABLES
        - value     The matplotlib floating-point date.
        - unit      The unit system to use for the Epoch.

        = RETURN VALUE
        - Returns the value converted to an Epoch in the specified time system.
        """
        # Delay-load due to circular dependencies.
        import matplotlib.testing.jpl_units as U

        secPastRef = value * 86400.0 * U.UnitDbl(1.0, 'sec')
        return U.Epoch(unit, secPastRef, EpochConverter.jdRef)

    @staticmethod
    def epoch2float(value, unit):
        """: Convert an Epoch value to a float suitible for plotting as a
              python datetime object.

        = INPUT VARIABLES
        - value    An Epoch or list of Epochs that need to be converted.
        - unit     The units to use for an axis with Epoch data.

        = RETURN VALUE
        - Returns the value parameter converted to floats.
        """
        return value.julianDate(unit) - EpochConverter.jdRef

    @staticmethod
    def duration2float(value):
        """: Convert a Duration value to a float suitible for plotting as a
              python datetime object.

        = INPUT VARIABLES
        - value    A Duration or list of Durations that need to be converted.

        = RETURN VALUE
        - Returns the value parameter converted to floats.
        """
        return value.seconds() / 86400.0

    @staticmethod
    def convert(value, unit, axis):
        """: Convert value using unit to a float.  If value is a sequence, return
        the converted sequence.

        = INPUT VARIABLES
        - value    The value or list of values that need to be converted.
        - unit     The units to use for an axis with Epoch data.

        = RETURN VALUE
        - Returns the value parameter converted to floats.
        """
        # Delay-load due to circular dependencies.
        import matplotlib.testing.jpl_units as U

        isNotEpoch = True
        isDuration = False

        if np.iterable(value) and not isinstance(value, str):
            if len(value) == 0:
                return []
            else:
                return [EpochConverter.convert(x, unit, axis) for x in value]

        if isinstance(value, U.Epoch):
            isNotEpoch = False
        elif isinstance(value, U.Duration):
            isDuration = True

        if (isNotEpoch and not isDuration and
           units.ConversionInterface.is_numlike(value)):
            return value

        if unit is None:
            unit = EpochConverter.default_units(value, axis)

        if isDuration:
            return EpochConverter.duration2float(value)
        else:
            return EpochConverter.epoch2float(value, unit)

    @staticmethod
    def default_units(value, axis):
        """: Return the default unit for value, or None.

        = INPUT VARIABLES
        - value    The value or list of values that need units.

        = RETURN VALUE
        - Returns the default units to use for value.
        """
        frame = None
        if np.iterable(value) and not isinstance(value, str):
            return EpochConverter.default_units(value[0], axis)
        else:
            frame = value.frame()

        return frame
